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At least 19 recordsLinked to original sources
PubMed1987

[Expression of the quantitative trait radius incompletus, temperature effects and localization of mobile genetic elements in Drosophila. II. Mobile genetic elements Dm-412].

Two "selection" sub-populations (ris- and ris+), as well as two "temperature" ones (ric113 and ric149) were earlier developed from the control ric sub-population with interrupted vein of the fly wing. All five sub-populations were investigated for hybridization of MGE Dm-412 with drosophila polytene chromosomes in situ. The tree of similarity of MGE Dm-412 hybridization patterns was built by the methods of matrix clusterization. The sub-populations with the most resembling expressions of characters (ris- and ric113, ris+ and ric149) were found to be also most similar in patterns of MGE localization and their changes. Nonrandomness of these changes was shown, the similarity of patterns being demonstrated to be mainly the result of the changes. There is evidence that such effects cannot be accounted for by genetic drift and independent stochastic changes in MGE localization.

Animals↗
PubMed2006

Mammalian small nucleolar RNAs are mobile genetic elements.

Small nucleolar RNAs (snoRNAs) of the H/ACA box and C/D box categories guide the pseudouridylation and the 2'-O-ribose methylation of ribosomal RNAs by forming short duplexes with their target. Similarly, small Cajal body-specific RNAs (scaRNAs) guide modifications of spliceosomal RNAs. The vast majority of vertebrate sno/scaRNAs are located in introns of genes transcribed by RNA polymerase II and processed by exonucleolytic trimming after splicing. A bioinformatic search for orthologues of human sno/scaRNAs in sequenced mammalian genomes reveals the presence of species- or lineage-specific sno/scaRNA retroposons (sno/scaRTs) characterized by an A-rich tail and an approximately 14-bp target site duplication that corresponds to their insertion site, as determined by interspecific genomic alignments. Three classes of snoRTs are defined based on the extent of intron and exon sequences from the snoRNA parental host gene they contain. SnoRTs frequently insert in gene introns in the sense orientation at genomic hot spots shared with other genetic mobile elements. Previously characterized human snoRNAs are encoded in retroposons whose parental copies can be identified by phylogenic analysis, showing that snoRTs can be faithfully processed. These results identify snoRNAs as a new family of mobile genetic elements. The insertion of new snoRNA copies might constitute a safeguard mechanism by which the biological activity of snoRNAs is maintained in spite of the risk of mutations in the parental copy. I furthermore propose that retroposition followed by genetic drift is a mechanism that increased snoRNA diversity during vertebrate evolution to eventually acquire new RNA-modification functions.

Animals↗
PubMed1995

Mobile genetic elements in mycobacteria.

Mobile genetic elements, ranging from plasmids and bacteriophages to insertion sequences and transposons, have come to play key roles in many aspects of basic and applied research in mycobacteriology. Plasmids and bacteriophages have been widely used as cloning vectors, especially for constructing recombinant vaccines based on bacille Calmette-Guérin (BCG); composite transposons have also been used for this purpose. At the same time, insertion sequences have proved invaluable for diagnostic and epidemiological studies, and transposon mutagenesis provides a useful method for inactivating and marking selected mycobacterial genes. Plasmids are commonly found in many mycobacterial species, notably M. avium, although not in M. tuberculosis; the biological significance of these plasmids (if any) is mostly unknown. Insertion sequences, and other repetitive elements, have also been characterized from many mycobacterial species. Special attention is paid to IS6110/IS986, from M. tuberculosis, and the IS900 family from M. avium and related organisms; the latter includes the recently described highly mobile element IS1110. The emphasis of the paper is on the molecular biology and significance of plasmids and insertion sequences/transposons, in mycobacteria and in bacteria of plasmids and insertion sequences/transposons, in mycobacteria and in bacteria in general, and their applications as cloning vectors and in transposon mutagenesis.

BCG Vaccine↗
PubMed1984

Mobile genetic elements in animal cells and their biological significance.

Mobile genetic elements were discovered by McClintock while analysing unstable mutations in maize. The structural and functional studies of such elements became possible after their cloning, first from the genome of Drosophila melanogaster. In particular, Ilyin et al. demonstrated the varying location of the described elements in D. melanogaster chromosomes, thus providing the first evidence of their mobility. Mobile elements comprise a significant part of the genetic material in D. melanogaster (not less than 10%). Several classes of mobile elements do exist. Mobile dispersed genetic elements (mdg elements) are among the best characterized ones. Mdg elements are represented in the genome by dozens of families, each consisting of 10-150 copies. They are very similar structurally to proviruses of endogenous retroviruses. In particular, the both contain long terminal repeats (LTRs). The nucleotide sequences of LTRs and their flanking sequences of several mdg elements were determined. Their analysis suggested that RNA reverse transcription should be involved in the mdg amplification. It has been found that putative transposition intermediates, i.e. extrachromosomal DNA copies of mdg elements, are synthesized by reverse transcriptase in D. melanogaster culture cells. Another type of mobile genes is represented by P factor and similar elements. P factor seems to encode 'transposase' participating in direct excision and insertion of P elements themselves as well as of other mobile genes (mdg and fold-back elements). Besides these 'active transposons' which encode the enzyme machinery for transposition, a number of other sequences which may be transposed are present in the genome. RNAs synthesized on such elements can serve as a template for reverse transcriptase, and the DNA formed can then be inserted at new sites of the genome. Among such sequences are the so-called short ubiquitous repeats: B1 and B2 in mouse genome and Alu in human genome. We found that, at least in several cases, B-type sequences were located at the 3' end of mRNA. Short repetitive sequences were also detected at the 3' end of certain mRNAs of D. melanogaster. Usually the transpositions of mobile genes occur very rarely. However, under certain conditions, for example, in hybrid dysgenesis, they become more frequent. The strain with a mutation in cut locus was obtained in hybrid dysgenesis. This mutation depends on an insertion of mdg4 at the cut locus. Genetic instability in this strain is maintained for a long time. 'Transposition bursts' were found to occur in some germ cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Mobile genetic elements in protozoan parasites.

Mobile genetic elements, by virtue of their ability to move to new chromosomal locations, are considered important in shaping the evolutionary course of the genome. They are widespread in the biological kingdom. Among the protozoan parasites several types of transposable elements are encountered. The largest variety is seen in the trypanosomatids-Trypanosoma brucei, Trypanosoma cruzi and Crithidia fasciculata. They contain elements that insert site-specifically in the spliced-leader RNA genes, and others that are dispersed in a variety of genomic locations. Giardia lamblia contains three families of transposable elements. Two of these are subtleomeric in location while one is chromosome-internal. Entamoeba histolytica has an abundant retrotransposon dispersed in the genome. Nucleotide sequence analysis of all the elements shows that they are all retrotransposons, and, with the exception of one class of elements in T. cruzi, all of them are non-long-terminal-repeat retrotransposons. Although most copies have accumulated mutations, they can potentially encode reverse transcriptase, endonuclease and nucleic-acid-binding activities. Functionally and phylogenetically they do not belong to a single lineage, showing that retrotransposons were acquired early in the evolution of protozoan parasites. Many of the potentially autonomous elements that encode their own transposition functions have nonautonomous counterparts that probably utilize the functions in trans. In this respect these elements are similar to the mammalian LINEs and SINEs (long and short interspersed DNA elements), showing a common theme in the evolution of retrotransposons. So far there is no report of a DNA transposon in any protozoan parasite. The genome projects that are under way for most of these organisms will help understand the evolution and possible function of these genetic elements.

Animals↗
PubMed2001

MGE-PCR: a novel approach to the analysis of Toxoplasma gondii strain differentiation using mobile genetic elements.

The position of mobile genetic elements (MGE) within eukaryotic genomes is often highly variable and we have exploited this phenomenon to develop a novel approach to strain differentiation in Toxoplasma gondii. Two PCR based strategies were designed in which specific primers were used to amplify T. gondii MGE's revealing information on element size and positional variation. The first PCR strategy involved the use of a standard two primer PCR while the second strategy used a single specific primer in a step-up PCR protocol. This approach was applied to T. gondii reference strains which were either acute virulent or avirulent to mice. The use of a standard two primer PCR reaction revealed the presence of a virulence related marker in which all avirulent strains possessed an additional 688 bp band. The single primer PCR strategy demonstrated that all virulent strains had identical banding patterns suggesting invariance within this group of strains. However, all avirulent strains had different banding patterns indicating the presence of a number of individual lineages within this group. The applicability and sensitivity of MGE-PCR in epidemiological studies was demonstrated by direct amplification of T. gondii from sheep tissue samples. All sheep isolates, tested in this way, gave identical banding patterns suggesting the presence of an endemic Toxoplasma strain on this farm.

Animals↗
PubMed2005

Molecular tools to detect the IncJ elements: a family of integrating, antibiotic resistant mobile genetic elements.

The IncJ group of enterobacterial mobile genetic elements, which include R391, R392, R705, R997 and pMERPH, have been shown to be site-specific integrating elements encoding variable antibiotic and heavy metal resistance genes. They insert into a specific 17-bp site located in the prfC gene, encoding peptide release factor 3, in Escherichia coli and other hosts. A key feature of known IncJ elements is the presence of a site-specific recombination module consisting of an attachment site on the element and an integrase-encoding gene of the tyrosine recombinase class, which promotes integration between the attachment site on the element and a similar site on the host chromosome. We have cloned and sequenced the integrases from a number of known IncJ elements and designed PCR primers for specific amplification of this gene. Using conserved regions of enterobacterial prfC genes upstream and downstream of the insertion site, and conserved sequences at the ends of the integrated IncJ elements, we have designed specific primers to amplify across the integrated IncJ attL and attR junction fragments. Alignment of over 30 enterobacterial prfC-like genes indicates that the primers designed to amplify attR junction would amplify IncJ element: host junctions from a wide variety of hosts. The IncJ elements have been shown to sensitise recA(+)E. coli K12 strains to UV irradiation. A simple and rapid procedure for demonstrating this effect is described. These tools should enable the rapid detection of such elements in clinical and environmental settings.

Attachment Sites, Microbiological↗
PubMed1985

Gene organization and target specificity of the prokaryotic mobile genetic element IS26.

The 820-bp mobile genetic element IS26 loses its ability to promote transpositional cointegration (1) by short deletions near the middle of the element causing shifts in both reading frames ORFI (left to right) and ORFII (right to left) and (2) by deletions causing substitutions of the C-terminus of ORFI but not affecting ORFII. The 702-bp ORFI is thus likely to code for the IS26 transposase. An 82-bp long sequence from the left end of IS26 contains a promoter-like structure in front of the start of ORFI at coordinate 64. In appropriately constructed plasmids, this sequence promotes the expression of the galK structural gene. The observation provides additional evidence for the functional relevance of ORFI. Neither the presence nor the absence of an intact IS26 element on the same plasmid affects measurably the degree of the galK gene expression by the IS26 promoter. Sequence comparison of 14 independent integration sites of IS26 and its relatives reveals no striking rules for target selection by the element, and the distrubtion of integration sites of IS26 on small multicopy plasmids is nearly random and independent of the local AT-content.

Base Sequence↗
PubMed1989

Transfer RNA genes: landmarks for integration of mobile genetic elements in Dictyostelium discoideum.

In prokaryotes and eukaryotes mobile genetic elements frequently disrupt the highly conservative structures of chromosomes, which are responsible for storage of genetic information. The factors determining the site for integration of such elements are still unknown. Transfer RNA (tRNA) genes are associated in a highly significant manner with different putative mobile genetic elements in the cellular slime mold Dictyostelium discoideum. These results suggest that tRNA genes in D. discoideum, and probably tRNA genes generally in lower eukaryotes, may function as genomic landmarks for the integration of different transposable elements in a strictly position-specific manner.

Base Sequence↗
PubMed2001

[Mobile genetic elements and their role in evolution of pathogenic bacteria].

The review discusses a role of mobile genetic elements in the evolution of pathogenic bacteria. Particularly great emphasis is placed on two recent thoroughly studied mobile genetic elements--the islets of pathogenicity and cassettes containing antibiotic resistant genes. The matters associated with the structural organization of these types of mobile elements, mechanisms of their translocations and involvement in the production of pathogenic bacteria are considered in detail. The data on the impact of macroorganisms on the horizontal dissemination of genetic information are discussed.

Bacteria↗
PubMed1984

Nucleotide sequence of the prokaryotic mobile genetic element IS30.

The complete nucleotide sequence of the mobile genetic element IS30, a resident of Escherichia coli K12, is 1221 bp long. A large open reading frame, preceded by possible transcription and translation control signals, could encode a basic protein of 383 amino acids which might presumably function as transposase. No large in-frame open reading frame is present on the opposite strand. The 26 bp long terminal inverted repeats have some sequence homology with the c-end of the phage Mu genome and with the terminal inverted repeats of the Halobacterium halobium insertion element ISH50. The IS30 sequence has no significant homology with any other sequenced prokaryotic insertion sequences.

Base Composition↗
PubMed1996

[Induction of transposition and excision of mobile genetic elements in Drosophila during isogenization].

Localization patterns of mobile genetic element (MGE) Dm412 were compared in chromosomes of ten isogenic lines and a heterogeneous control line riC of Drosophila. Isogenization was shown to induce MGE transpositions and excisions. Rates of induced transpositions and excisions were, respectively, 0.35 and 0.13 per site per haploid genome per isogenization, which is significantly (by two to three orders of magnitude) higher than corresponding rates in the control line. These values are also higher by an order of magnitude than previously obtained rates of transposition induction by means of heat shock treatment and gamma-irradiation of isogenic lines. In the average haploid genome of the original line, nc = 22.14 of the occupied Dm412 sites correspond to 11.9 transpositions and 4.6 excisions generated by isogenization. Calculated for the genomic system of copia-like MGE, these rates are approximately 105 and 39 events per approximately 300 initial MGE positions. Apparently, these rates exceed the "catastrophic limit of transpositions and excisions." A hypothesis on the role of inbreeding as genomic stress in induction of transpositions and excisions was proposed. Inbreeding is assumed to increase cell concentration of defective proteins, acting via the system of heat shock response-a general system of cell response to external and physiological stresses.

Animals↗
PubMed1989

Mobile genetic elements in Drosophila melanogaster (recent experiments).

Recent data obtained in the authors' laboratories concerning the behaviour of mobile genetic elements of Drosophila melanogaster are reviewed. It was found that the mobile element jockey represents the typical LINE element. It is efficiently transcribed in D. melanogaster cells in flies and in culture. Transcription is initiated from the +1 nucleotide of jockey and depends on an internal promoter. This is the first case of an internal promoter being used by RNA polymerase II. Several events which take place during the transposition bursts in ctMR2 family of strains were described. Among them are the removal of mobile dispersed genetics (mdg) elements (with solo long terminal repeat (LTR) remaining at the site of excision), complete removal of an mdg element, and reinsertion of the same mdg to the same place either in the presence or in absence of solo LTR sequence. Finally, the formation of deletions was observed. A 462-bp deletion destroying the white locus can be further repaired (w+ reversion). Thus, transposition bursts include many different genetic events. A novel system of prolonged genome destabilization was described. It depends on mobilization of a new mobile element called Stalker. After certain crosses Stalker actively moves for dozens of generations giving rise to large numbers of insertion mutations. Several novel genes were detected using mobilized Stalker. They include a modifier of mdg4 and six enhancers of yellow mutations.

Animals↗
PubMed2005

Regulation of a Bacillus subtilis mobile genetic element by intercellular signaling and the global DNA damage response.

Horizontal gene transfer contributes to the evolution of bacterial species. Mobile genetic elements play an important role in horizontal gene transfer, and characterization of the regulation of these elements should provide insight into conditions that influence bacterial evolution. We characterized a mobile genetic element, ICEBs1, in the Gram-positive bacterium Bacillus subtilis and found that it is a functional integrative and conjugative element (ICE) capable of transferring to Bacillus and Listeria species. We identified two conditions that promote ICEBs1 transfer: conditions that induce the global DNA damage response and crowding by potential recipients that lack ICEBs1. Transfer of ICEBs1 into cells that already contain the element is inhibited by an intercellular signaling peptide encoded by ICEBs1. The dual regulation of ICEBs1 allows for passive propagation in the host cell until either the potential mating partners lacking ICEBs1 are present or the host cell is in distress.

Bacillus↗
PubMedDate not supplied

[Cloning and expression in Escherichia coli of reverse transcriptase coded by the mobile genetic element jockey].

The mobile element jockey is similar in structural organization and coding potential to the LINEs of various organisms. Current models of the mechanism of transposition involve reverse transcription of an RNA intermediate and utilization of element-encoded proteins. As it is demonstrated here, a 2.23 kb DNA fragment from the region of the jockey encoding the putative reverse transcriptase, was stably introduced into the expression system under inducible control of the Escherichia coli lac regulatory elements. We describe the expression of the 92 kDa protein and identify this polypeptide alone as authentic jockey reverse transcriptase based on some of its physical and enzymic properties. The jockey polymerase demonstrates RNA-directed and DNA-directed DNA polymerase activities, but lacks detectable RNase H, has a temperature optimum at 26 degrees C, requires Mg2+ or Mn2+ as a cofactor and is inactivated by sulfhydryl reagent. The enzyme prefers poly(rC) and poly(rA) as template and "activated" DNA is not effective. The results of this work suggest that the RNA-directed DNA polymerase coded by jockey elements may be involved in the transcription of the elements.

Amino Acid Sequence↗
PubMed1987

[Presence in the mobile genetic elements of regions homologous to the heat shock regulatory site].

The results of contextual analysis of 13 different mobile genetical elements (MGE) MDG1, MDG2, MDG3, MDG4, HOBO, P, F, MDG 17.6, H. M. S. Beagle, CIN1, BS1, TDD1, EV1 are presented. A search for regions revealing marked and statistically non-random homology with the consensus sequence of the heat-shock regulatory site (HSRS) has been carried out in these elements. Seven MGE (MDG1, MDG4, HOBO, P, CIN1, BS1, EV1) were shown to contain the regions of non-random homology with the HSRS consensus and the real HSRS. Evolutionary significance of connection between the environment and genetical cell system, based on the transcriptional activation of mobile genetical elements by heat-shock and some other factors, has been discussed.

Animals↗
PubMed2006

An analysis of mobile genetic elements in three Plasmodium species and their potential impact on the nucleotide composition of the P. falciparum genome.

BACKGROUND: The completed genome sequences of the malaria parasites P. falciparum, P. y. yoelii and P. vivax have revealed some unusual features. P. falciparum contains the most AT rich genome sequenced so far--over 90% in some regions. In comparison, P. y. yoelii is approximately 77% and P. vivax is approximately 55% AT rich. The evolutionary reasons for these findings are unknown. Mobile genetic elements have a considerable impact on genome evolution but a thorough investigation of these elements in Plasmodium has not been undertaken. We therefore performed a comprehensive genome analysis of these elements and their derivatives in the three Plasmodium species. RESULTS: Whole genome analysis was performed using bioinformatic methods. Forty potential protein encoding sequences with features of transposable elements were identified in P. vivax, eight in P. y. yoelii and only six in P. falciparum. Further investigation of the six open reading frames in P. falciparum revealed that only one is potentially an active mobile genetic element. Most of the open reading frames identified in all three species are hypothetical proteins. Some represent annotated host proteins such as the putative telomerase reverse transcriptase genes in P. y. yoelii and P. falciparum. One of the P. vivax open reading frames identified in this study demonstrates similarity to telomerase reverse transcriptase and we conclude it to be the orthologue of this gene. CONCLUSION: There is a divergence in the frequencies of mobile genetic elements in the three Plasmodium species investigated. Despite the limitations of whole genome analytical methods, it is tempting to speculate that mobile genetic elements might have been a driving force behind the compositional bias of the P. falciparum genome.

Amino Acid Sequence↗